ANTHOZOA—TETRACORALLA. 



69 



42. A. davidsoni E. & H. (Fig. 106.) Devonic. 



Centers of calices abruptly depressed, diameter about 10 mm. 

 Septa alternating in length but equal in thickness at the margin 

 of the calyx, carinae abundant. 



Common in strata of Hamilton age in Michigan, Iowa, etc., and 



Fig. 105. Aceryularia rugosa (after 

 Simpson). 



Fig. 106. Acervularia davidsoni (after 

 Simpson). 



also found in strata of somewhat earlier age at the Falls of the 

 Ohio and elsewhere. 



XVIII. Phillipsastr^ea D'Orbigny. 



Coral heads composed of large confluent corallites, similar to 



compound Heliophytlum, but without the dividing walls. Calicular 



surfaces flat, except at the center, where an abrupt depression, 



usually surrounded by an elevated rim occurs. Longer septa 



uniting at the center, 

 shorter stop at the central 

 pit. Dev.-Carb. 



43- P- gig a s Owen. 



Devonic. 

 Large, the calices over 

 20 mm. in diameter and 

 their outlines defined; cen- 

 tral pit large. 



In the Onondaga lime- 

 stone of New York, Can- 

 ada, Michigan and the Falls of the Ohio. Hamilton of Michigan. 



44. P. verneuilli E. & H. (Fig. 107.) Devonic. 



Smaller, corallites from 10-15 mm. in diameter. 



Fig. 107. Phillipsastrcea verneuilli (after 

 Billings). 



